In such devices that are used in practice, for instance for closing PET bottles with screw caps, for example, of the type known from DE-A-101 24 659, the closing element used must be screwed together with a fitting sleeve downwards out of the closing head upon change to another type of screw cap. Since different bottle conveying and treating components, e.g. round neck-guiding plates, of which at least some must be exactly adjusted to the closing head, are installed underneath the closing head and relatively close to said head, the change of the closing element requires the disassembly of at least some components so as to provide space and access downwardly, as well as subsequent new adjusting operations. This calls for considerable set-up times and is a difficult job carried out with tools. Since it often happens that even bottles of the same producer have different screw caps, although the bottles are always the same, i.e. after a closing-element change they would actually not require any adjusting of the components adjoining the closing head, the long setting times matter a lot. Moreover, with frequent closing-element changes there arises the risk of seizure of the thread with which the closing element is fixed in the closing head.